1. Field of the Invention
The present invention relates to a wireless node that learns a time zone where there are sufficient wireless resources in an autonomous distributed manner and sets dynamically a communication time at this time zone thereby to carry out time-division transmission and reception of non-realtime data traffic.
2. Description of the Related Art
There are various kinds of data traffic transmission and reception performed by wireless data communication nodes, such as web browsing, transmission and reception of streaming video, transmission and reception of electronic mails and transmission and reception of huge data files. Japanese Patent Application Laid-Open No. 2003-169363 and “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 8: Medium Access Control (MAC) Quality of Service Enhancements”, IEEE Std. 802.11e, 2005 disclose the techniques of focusing attention on the degree of requiring the data traffic to be in realtime and allocating wireless resources (time, frequency, power) by priority to data traffic of higher priority that requires high level of realtime. In other words, in these techniques of related art, data traffic that is even of low priority and does not require realtime at all is inevitably allocated with wireless resources, and therefore, the wireless resources are consumed.
In this way, in the techniques of allocating wireless resources based on the priority set to the data traffic, the wireless resources are inevitably allocated to all data traffic sources according to the priority, irrespective of the network state. Therefore, even in the event of network congestions, wireless resources are allocated corresponding to data traffic that requires no realtime. For this reason, from the point of view of operators who operate wireless network (telecommunications carriers), it is not preferable that unurgent data traffic that requires no realtime needs to be held though there is congestion, and wireless resources, which should be allocated to other data traffic requiring realtime communication, are consumed in vain.
From the point of view of users that use wireless access network, wireless resources, which should be allocated to users of an application that requires realtime communication are undesirably allocated to a user of an application that does not require realtime communication that is, “unurgent application of which downloading may be finished at any future time”. Further, a user of an application that does not require realtime communication may desire reduction in communication charge in return for the realtime communication.
To address this technical problem, the inventors of the present invention have invented a system for carrying out time-division transmission and reception of data traffic that does not require realtime using a off-peak time zone where there are sufficient wireless resources and filed a patent application (Japanese Patent Application No. 2009-70456).
The congestion level of wireless resources has geographical dependency. The congestion level of a business area is high for typical business hours (for example, 8 to 19 o'clock), while the congestion level of a residential area tends to be high after the business hours, in the middle of the night. Accordingly, for users who work in the business area and return to the residential area, the time zone between the midnight and morning is the off-peak time zone and for users who work based in the residential areas, the typical business hours are the off-peak time zone.
In this way, as the congestion level of wireless resources completely depends on behavior patterns of users, it is difficult to determine a fixed off-peak time zone of wireless resources in advance.
On the other hand, when an attention is focused on individual users, each user often repeats the same behavior pattern at intervals of 24 hours and daily variation of wireless resources at intervals of 24 hours can be often observed for every user. Accordingly, if the congestion level of wireless resources can be estimated in consideration of this periodicity, the communication time of non-realtime data can be optimized.